1. Field of the Invention
The present invention relates to an apparatus and method for producing a metallic ribbon of an amorphous metal or the like.
2. Description of the Related Art
As a method for producing a metallic ribbon, a single roll method using a single cooling roll is most popular at present. FIG. 33 shows a principal portion of a conventional apparatus for producing a metallic ribbon by using the single roll method.
The single roll method comprises blowing a melt 103 out of a melt nozzle 102 adjacent to the top of the cooling surface of a cooling roll 101, which is rotated at high speed, to draw out the melt 103 in the rotation direction (the direction of arrow A) of the cooling roll while rapidly solidifying it by the cooling surface of the cooling roll 101.
The melt 103 blown out of the melt nozzle 102 forms a puddle 104 between the end of the melt nozzle 102 and the cooling surface of the cooling roll 101, and the melt 103 is successively drawn out of the puddle 104 with rotation of the cooling roll 101, and rapidly solidified on the surface of the cooling roll 101 to continuously form a ribbon 105.
Where the material supplied in the single roll method has a highly oxidizable composition, the melt nozzle 102 is clogged due to oxidation of the material, hindering ejection of the melt.
In order to solve the problem of a conventional single roll method, a method is proposed in which the whole apparatus for producing a metallic ribbon is arranged in a chamber in which the oxygen concentration near the melt nozzle is deceased by an inert gas atmosphere, thereby preventing oxidation of material.
The method of forming an inert gas atmosphere in the chamber is very effective means for preventing clogging of the melt nozzle, but has a problem of workability because the whole apparatus is arranged in the chamber. For example, the conventional single roll method requires a complicated work comprising opening the chamber to fill a melt furnace or crucible with a metal mother material master alloy in each time of charge, closing the chamber, and then substituting air in the chamber with an inert gas atmosphere.
There is also a problem in which an additional equipment for holding an inert gas atmosphere in the chamber is expensive.
The present invention has been achieved for solving the above problems, and an object of the invention is to provide an apparatus for producing a metallic ribbon which can decrease the oxygen concentration of the atmosphere near a melt nozzle without providing a large-scale additional equipment exhibiting low workability, such as a chamber.
Unlike a conventional method, if only the vicinity of the melt nozzle can be brought into an inert gas atmosphere for decreasing the oxygen amount in order to prevent clogging of the melt nozzle, the whole apparatus for producing a metallic ribbon need not be placed in an inert gas atmosphere. Equipment in which only the vicinity of the melt nozzle is brought into an inert gas atmosphere permits improvement in workability and a decrease in equipment cost, as compared with a conventional chamber.
As a result of research with consideration of this point, the inventors found that by providing, at appropriate positions, air-cutoff means for preventing air from flowing into the periphery of the melt nozzle by rotation of the cooling roll, and gas flow means for supplying an inert gas to the periphery of the melt nozzle, the oxygen amount of the periphery of the melt nozzle can effectively be decreased.
An apparatus for producing a metallic ribbon of the present invention is achieved on the basis of the above findings. The apparatus comprises a cooling roll having a cooling surface for cooling a metal melt, a melt nozzle facing the cooling surface with a predetermined gap therebetween, roll periphery air-cutoff means which covers at least a portion of the periphery of the cooling roll and at least the melt blowout end of the melt nozzle, for preventing an inflow of air due to rotation of the cooling roll, wherein the body of the melt nozzle is arranged outside the roll periphery air-cutoff means.
In the apparatus for producing a metallic ribbon of the present invention, the roll periphery air-cutoff means is provided on at least the front side and the rear side on the basis of the melt nozzle (referred to as xe2x80x9cthe front sidexe2x80x9d and xe2x80x9cthe rear sidexe2x80x9d hereinafter) in the rotation direction of the cooling roll, and an air retention portion is provided on the front side in the rotation direction of the cooling roll.
The air retention portion may be provided either inside or outside the roll periphery air-cutoff means. The air retention portion preferably has an aperture area larger than the aperture area of the roll periphery air-cutoff means. In addition, the inside of the air retention portion may be divided by a plurality of partitions.
In the apparatus for producing a metallic ribbon of the present invention, the roll periphery air-cutoff means comprises at least a roll face air-cutoff plate provided ahead of the cooling roll on the front side in the rotation direction thereof, a pair of front air-cutoff plates provided on both sides of the cooling roll on the front side in the rotation direction thereof so as to hold the cooling roll therebetween and contact the roll face air-cutoff plate, a roll top air-cutoff plate located above the cooling roll so as to extend from the front side to the rear side in the rotation direction of the cooling roll and contact the upper edges of the roll front air-cutoff plates, and a roll surface air-cutoff plate provided on the rear side in the rotation direction of the cooling roll so as to contact the cooling surface of the cooling roll, wherein the roll top air-cutoff plate is provided in such a manner that it approaches the cooling surface of the cooling roll in the direction opposite to the rotation direction of the cooling roll, and the melt blowout end of the melt nozzle is passed through a nozzle mounting hole provided in the roll top air-cutoff plate so as to face the cooling surface of the cooling roll.
The roll top air-cutoff plate preferably evenly extends from the frond side in the rotation direction of the cooling roll to the cooling surface.
Also the roll top air-cutoff plate may extend from the frond side in the rotation direction of the cooling roll to the cooling surface in such a manner that it is curved along the inside of the roll periphery air-cutoff means.
Furthermore, at least one partition may be provided on the roll top air-cutoff plate so as to project into the roll periphery air-cutoff means.
Further, a passage hole is preferably provided in the roll face air-cutoff plate to pass the metallic ribbon formed by cooling with the cooling roll therethrough.
The apparatus for producing a metallic ribbon of the present invention further comprises gas flow supply means for supplying inert gases to the periphery of the melt nozzle.
The gas flow supply means is preferably provided at two positions on each of the front side and the rear side in the rotation direction of the cooling roll on the basis of the melt nozzle. Particularly, the two gas flow supply means arranged on the rear side in the rotation direction of the cooling roll preferably comprise one arranged so that a slit thereof faces the melt nozzle end, and the other arranged between the melt nozzle and the one gas flow supply means to supply a gas flow onto the gas flow supplied from the one gas flow supply means.
The gas flow velocity of the gas flow supply means is preferably 2 to 80 m/sec, and the gas flow rate is preferably 200 to 1400 l/min.
The inventors also found that by providing a plurality of gas flow supply means preferably including first gas flow supply means and second gas flow supply means, the oxygen amount of the periphery of the melt nozzle can effectively be decreased.
Namely, the apparatus for producing a metallic ribbon in which a metal melt is cooled by blowing it toward the cooling surface of the rotating cooling roll to obtain a metallic ribbon, comprises the cooling roll; the melt nozzle for blowing the metal melt toward the cooling surface with a gap between the melt nozzle and the cooling roll; air-cutoff means which covers from at least the melt blowout end of the melt nozzle to at least the position where the metallic ribbon is separated from the cooling surface, along the rotation direction of the cooling roll, for preventing an inflow of air due to rotation of the cooling roll; roll surface air-cutoff means located behind the position where the melt nozzle and the cooling roll are opposed to each other, in the rotation direction of the cooling roll so as to contact the cooling surface, for cutting off an inflow of air into the periphery of the melt nozzle along the cooling surface due to rotation of the cooling roll; roll periphery air-cutoff means extending from at least the position where the metallic ribbon is separated from the cooling surface to the position where the roll surface air-cutoff means is provided, along the rotation direction of the cooling roll so as to surround the cooling roll and cover the cooling surface with a gap between the roll periphery air-cutoff means and the cooling surface; first gas flow supply means for supplying an inert gas to the periphery of the melt nozzle; and second gas flow supply means provided between the position where the metallic ribbon is separated from the cooling surface and the position where the air-cutoff means is provided, for supplying an inert gas to the cooling surface with a gap between the second gas flow supply means and the cooling surface.
The body of the melt nozzle is preferably arranged outside the roll periphery air-cutoff means.
In the above-described apparatus for producing a metallic ribbon of the present invention, the air-cutoff means comprises at least a roll face air-cutoff plate provided at a position forward of the melt nozzle on the front side in the rotation direction of the cooling roll; a pair of roll front air-cutoff plates provided on both sides of the cooling roll at a position forward of the melt nozzle in the rotation direction of the cooling roll so as to hold the cooling roll therebetween and contact the roll face air-cutoff plate; a roll top air-cutoff plate located above the cooling roll so as to extend from the front side to the rear side in the rotation direction of the cooling roll and contact the upper edges of the roll front air-cutoff plates; and a pair of roll side air-cutoff plates provided so as to hold the cooling roll therebetween and contact the roll front air-cutoff plates and the roll periphery air-cutoff means; wherein the roll top air-cutoff plate is provided in such a manner that it approaches the cooling surface of the cooling roll in the direction opposite to the rotation direction of the cooling roll, and the melt blowout end of the melt nozzle is arranged so as to pass through the nozzle mounting hole provided in the roll top air-cutoff plate and face the cooling surface of the cooling roll.
The roll top air-cutoff plate preferably flatly extends from the front side in the rotation direction of the cooling roll to the cooling surface.
Also the roll top air-cutoff plate may extend from the front side in the rotation direction of the cooling roll to the cooling surface in such a manner that it is curved along the inside of the roll periphery air-cutoff means.
Furthermore, at least one partition may be provided on the roll top air-cutoff plate so as to project into the roll periphery air-cutoff means.
Further, a passage hole is preferably provided in the roll face air-cutoff plate so that the metallic ribbon formed by cooling with the cooling roll is passed therethrough.
The flow rate of the first gas flow supply means is preferably 200 to 400 l/min.
The flow rate of the second gas flow supply means is preferably 150 to 350 l/min.
The gas flow supply means is preferably provided at two positions on each of the front side and the rear side in the rotation direction of the cooling roll on the basis of the melt nozzle. Particularly, the two gas flow supply means arranged on the rear side in the rotation direction of the cooling roll preferably comprise one arranged so that a slit thereof faces the melt nozzle end, and the other arranged between the melt nozzle and the one gas flow supply means to supply gas flow onto the gas flow supplied from the one gas flow supply means.
The apparatus for producing a metallic ribbon of the present invention further comprises an air retention portion provided at a position forward of the melt nozzle in the rotation direction of the cooling roll.
The air retention portion may be provided either inside or outside the roll periphery air-cutoff means. The air retention portion preferably has an opening area larger than the opening area of the roll periphery air-cutoff means. In addition, the inside of the air retention portion may be divided by a plurality of partitions.
As the inert gas, at least two inert gases are preferably used, and inert gases of N2, He, Ar, Kr, Xe and Rn are more preferably used.
The apparatus for producing a metallic ribbon of the present invention further comprises a sixth gas flow nozzle provided so as to surround the end of the melt nozzle so that when a gas flows from many holes provided at positions slightly inward of the center between the outer periphery and inner periphery of the sixth gas flow nozzle to surround the melt nozzle, the oxygen concentration in the vicinity of the melt nozzle can be further decreased by the sixth gas flow from the six gas flow nozzle.
The sixth gas flow nozzle may have a plurality of holes provided in a ring at the center between the outer and inner diameters thereof, or a ring slit in place of the holes. The sixth gas flow nozzle may be formed to a spiral shape or a double shape in which the melt nozzle is surrounded.
The apparatus for producing a metallic ribbon of the present invention further comprises a first gas flow nozzle directed toward the end of the melt nozzle in the direction substantially normal to the cooling roll, for flowing an inert gas heavier than the inert gases supplied from the other gas flow nozzles; and a second gas flow nozzle provided between the melt nozzle and the first gas flow nozzle, for providing a gas flow onto the gas flow from the first gas flow nozzle.
The gas flow rate of the first gas flow supply means is preferably 200 to 600 l/min.
The present invention also provides a method of producing a metallic ribbon comprising rapidly cooling an alloy melt by blowing the alloy melt out of a melt nozzle, which faces a cooling surface of a cooling roll, toward the rotating cooling roll with a predetermined gap held between the cooling roll and the melt nozzle to form a metallic ribbon, wherein the alloy melt is blown toward the cooling roll to form a metallic ribbon with the air-cutoff means provided so as to cover at least a portion of the periphery of the cooling roll and at least the melt blowout end of the melt nozzle, for preventing an inflow of air due to rotation of the cooling roll.
In the production method, the metal alloy is more preferably blown out with the inert gas supplied to the periphery of at least one of the melt nozzle and the cooling roll, to form a metallic ribbon.
The inert gas may be supplied from a plurality of gas flow supply means, and a metallic ribbon is more preferably formed under the supply of at least two inert gases.
As the two inert gases, N2 and Ar are more preferable.